Low profile rotary switch with detent in the bushing

ABSTRACT

A panel mounted low profile rotary switch ( 100 ) contains a detent mechanism ( 120 ) mounted in a bushing ( 110 ). In a preferred class of embodiments, the detent sub-assembly comprises a single spring ( 220 ) positioned in parallel within the vertical extending shaft ( 130 ). The force exerted by the spring is manually adjusted by a set screw ( 210 ) to provide the desired downward applied vertical force on a plunger ( 230 ). The plunger, preferably a pointed cylinder, applies pressure to detent balls ( 240 ) causing the detent balls to move radially outward and engage rotor cams located on the inner surface of the detent mechanism.

This application claims priority to PCT patent application numberPCT/US02/35610 filed on 5 Nov. 2002.

FIELD OF THE INVENTION

The field of the invention is electromechanical rotary switches.

BACKGROUND OF THE INVENTION

A rotary electromechanical switch is generally defined as a device thathas a rotating shaft connected to one terminal capable of making orbreaking a connection to one or more other terminals. A rotaryelectromechanical encoder includes the overall characteristics of arotary switch, but has additional mechanical movements. In any case, auser typically manipulates the switch to manually select a circuit.

Rotary switches and encoders are often mounted upon panels and othersupporting structures in order that a user may control an electricaldevice. It is common for a portion of the switch to be on one side ofthe panel (the user side) and another portion of the switch to be on theother side of the panel (the inside). In many instances, the onlyportion of a switch that is on the user's side of the panel is a sectionof the shaft and a knob or other actuating means. Generally, the bulk ofthe switch is on the inside of the panel. For many years this type ofconfiguration was sufficient, but over time the size of electricaldevices has become increasingly smaller and there has become a need toreduce the size of the switch—especially that portion on the inside ofthe panel.

In order to meet the needs of smaller devices having less room under thepanel, the size of the components of the switches have also becomesmaller. Yet, because these switches are comprised in part of mechanicalcomponents, there remained a practical limit as to how small they couldbecome while still remaining useful. There became a need for differentdesigns rather than just a reduction in the size of the components. Onesuch design is taught in U.S. Pat. No. 4,454,391 to Olsson (June 1984).Olsson describes a low profile dip switch used on an integrated circuitboard in which the actuating member of the dip switch is set within thebody of the switch. By reducing the vertical profile of the switch, alower overall footprint may be achieved for a board. The switch designtaught by Olsson, however, does not address design problems related topanel mounted switches. Another patent which addresses problems in thedesign of switches is described in U.S. Pat. No. 6,312,288 to Genz etal. (November 2001). Genz teaches a low profile combination switch andconnector assembly. While the switch described by Genz may have resultedin a lower overall profile of the combined components, this switch stilldoes not address problems of panel mounted switches, specifically thoseproblems due to limited space under the panel.

U.S. Pat. No. 6,043,855 to Grave (March 2000) is directed towardswitches that mount on a bezel surrounding an LCD which is located on anavionics panel in an aircraft. The '855 patent teaches a design in whichthe detent is at least partially positioned in the knob of the switch.Still, the design of the '855 patent has its shortcomings: the detent ishoused by the knob such that if the knob were to be displaced, theswitch would not function or would function improperly; the detent isnot entirely within the knob; the design requires two springs; and thesprings are mounted vertically adding to the overall vertical profile ofthe knob.

As electronic devices become even smaller, there is a need for morecompact and efficient designs.

SUMMARY OF THE INVENTION

The inventive subject matter is a panel mounted low profile switchhaving a detent sub-assembly housed in a bushing. The portion of thebushing housing the spring is in substantial planar relation with thepanel within which the switch is mounted.

In some embodiments the detent sub-assembly comprises a single springpositioned vertically in the vertical extending shaft.

Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of an exploded rotary switch.

FIG. 2 is a perspective view of an exploded rotary switch.

FIG. 3 is a perspective view of an exploded rotary switch.

FIG. 4 is a vertical cross-section of a portion of the switch of FIG. 1.

FIG. 5 is an exploded view of a bushing and detent mechanism in theswitch of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 depicts a rotary switch 100 generally comprised of a bushing 110,a detent mechanism 120, a shaft 130, an electrical contact 140, and aprinted circuit board (PCB) 150.

Bushing 110 is comprised of a threaded upper portion 112 and a lowerportion 114. As defined herein, a bushing is a component of a switchthat is used to hold the switch to a panel (e.g. a control borad)through which the switch is mounted. A preferred bushing has an upperportion that extends through a hole in the panel and a lower portionthat contacts the underside (i.e. non-user side) of the panel. In FIG.1, bushing 110 has a threaded upper portion 112 that extends throughhole 164 in the panel 160. In order to facilitate holding of the switchto the panel, the lower portion 114 is of a diameter and/or shape thatwill not fit through the hole 164 in the panel 160. A lock washer 172 isplaced over the upper portion of the bushing 112 and the capture nut 170is threaded to the upper portion 112 in order to hold the switch to thepanel. It is not required that a bushing be threaded and that a nut beused to hold the switch to the panel as non-threaded bushings may alsobe used. A non-threaded bushing can be held to the panel in other ways,for example by using rivets or compression fittings.

It is generally contemplated that a bushing should not rotate, andherein there are provided means for substantially prohibiting suchrotational movement. One such means is a pin/aperture configuration inwhich the pin 116 fits snugly within an aperture 162 in the panel. Inanother class of embodiments, it may be advantageous to have a “D”shaped hole (opening) in the panel, such “D” shaped hole cooperatingwith a flat sided bushing to prevent rotation. It should be understoodthat any combination of suitable shapes and sizes will suffice so longas the combination substantially prohibits rotational movement. Forexample, the hole in the panel and the associated upper portion of thebushing may have two or more flat sides.

A detent sub-assembly is comprised of the detent mechanism 120 havingrotors 121, a spring 122, and a ball 124. Further analysis of the switchdepicted in FIG. 1 reveals a single spring detent sub-assembly in whichthe spring 122 is horizontally disposed (i.e perpendicular to theshaft). The spring is in contact (direct or indirect) with at least oneball 124. Note that in some horizontal single spring embodiments twoballs may be utilized, one on each end of the spring. In any case, theball 124 is biased toward the inner surface of the detent mechanism 120.Along the inner surface of the detent mechanism are rotor cams (i.e.cylindrical lobes) 121. As the shaft 130 of the switch is rotated, theball(s) rotates about the rotor cams as the electrical contact 140rotates about the PCB 150. The detent sub-assembly is housed within thebushing 110, preferably within the upper portion of the bushing 112.However, it is envisaged that a portion of the detent sub-assembly mayextend into the lower portion of the bushing.

It is preferred that the detent mechanism be prevented from rotationwithin the bushing. Along these lines, the detent mechanism 120 can havean extrusion 126 that engages a notch 118 on the inner surface of thebushing thereby preventing such rotation. Of course, the shaft isintended to rotate, however, it can be advantageous to limit therotation of the shaft. Limiting rotation of the shaft can beaccomplished by using a pin 132 to limit the degree of rotation as afunction of the size of a notch 128 in the detent mechanism. By limitingthe rotation of the shaft, the available switch settings can be limited.

An electrical contact 140 (e.g. switch wipers or brushes) is mounted ona non-conductive disc 135 (i.e. dielectric) and the contact 140cooperates with the circuit configuration on the PCB 150. The PCB 150 isanchored to the bushing 110 by metal rivets 190 or other connectors,however it should be noted that anchoring of the PCB to the bushing isnot a requirement. Although not depicted, a PCB can contain additionalelectronic components (e.g chips, pins, leads, and so forth) that mayinterface with components other than the switch. Setting of a switchposition, therefore, is generally a function of the interaction amongthe detent sub-assembly, the shaft, the electrical contact and the PCB.

Turning now to FIG. 2, an alternative embodiment includes a verticalspring 220 (i.e. parallel to the shaft), a set screw 210, and a plunger230. The single vertical spring 220 is housed within the shaft and iselongated in the same direction as the shaft. The set screw 210 isthreaded into the upper portion 212 of the shaft 130 thereby causing theplunger to exert outward pressure on the balls 240. The outward pressurebiases the balls in the direction of the rotor cams on the inner surfaceof the detent mechanism 120. It should be noted that outward tensionagainst the balls can be adjusted by threading or unthreading the setscrew. As the set screw is threaded in, the plunger is forced downward(toward the PCB) and the balls are pushed outward. Of course,unthreading the set screw will have the opposite effect. A plunger ispreferably cylindrical in shape and pointed. The preferred plunger notonly provides uniform pressure to the balls, but it also allows for morethan two balls to be used with a single spring.

A switch can be configured to set a plurality of electrical settings.FIG. 3 depicts a multiple deck switch having a vertical springconfiguration. The embodiment of FIG. 3 has two sets of contacts and twoPCBs. The first set of contacts 140 is attached to a non-conductive(dielectric) disc 310 which is further coupled to the shaft 130. Asecond non-conductive disc 320 is also coupled to the shaft 130 and isfurther coupled to a second set of contacts 330. A spacer 340 providesinsulation between the PCBs.

Functionally, the shaft of a switch is generally rotated by manualmovement in order to set a switch position. Switch positions are definedby the rotor cams (lobes) in the detent mechanism. Upon rotation of theshaft, a ball protruding from the shaft will set in the area between tworotor cams thereby defining a switch position. A user of the switch willbe able to feel the ball set between the rotor cams. As a ball rotatesabout the inner surface of the detent mechanism, the contacts formelectrical connections based on the relationship between the contact andthe PCB. While the switches enumerated here are shown with a stop pin tolimit the rotation of the shaft, this is not a requirement as someswitches will allow 360 degree rotation in both directions.

Methods of use include mounting a rotary switch such that the detentsub-assembly is in planar relation to a panel. Since most of the upperportion of the bushing is on the user's side of the panel, however, thedetent sub-assembly may be substantially on the user's side of the panelrather than in a plane with the panel. Additionally, there may even be aportion of the detent sub-assembly which extends underside of the panel.Thus, a single detent sub-assembly may be positioned such that a portionof the detent sub-assembly is above the panel, a portion is parallelwith the panel, and a portion is below the panel.

Thus, specific embodiments and applications of a low profile switch witha detent in the bushing have been disclosed. It should be apparent,however, to those skilled in the art that many more modificationsbesides those already described are possible without departing from theinventive concepts herein. The inventive subject matter, therefore, isnot to be restricted except in the spirit of the appended claims.Moreover, in interpreting both the specification and the claims, allterms should be interpreted in the broadest possible manner consistentwith the context. In particular, the terms “comprises” and “comprising”should be interpreted as referring to elements, components, or steps ina non-exclusive manner, indicating that the referenced elements,components, or steps may be present, or utilized, or combined with otherelements, components, or steps that are not expressly referenced.

1. A panel mounted rotary switch, comprising: a bushing having an upperportion that extends through the panel to a user's side and a lowerportion that remains beneath the panel and prevents the bushing frommovement toward the user's side; and a detent sub-assembly housed in theupper portion of the bushing.
 2. The panel mounted rotary switch ofclaim 1, having a shaft that couples a knob on the user's side with anelectrical contact beneath the panel.
 3. The panel mounted rotary switchof claim 2, wherein operation of the detent sub-assembly is independentof the knob.
 4. The panel mounted rotary switch of claim 1, wherein thedetent sub-assembly is positioned an planar relation to the panel. 5.The panel mounted rotary switch of claim 1, wherein the bushing isprevented from rotational movement by an engagement with the panel. 6.The panel mounted rotary switch of claim 5, wherein the lower portion ofthe bushing has a stop pin that fits within an aperture on the panel. 7.The panel mounted rotary switch of claim 6, wherein the detentsub-assembly is prevented from rotational movement by an engagement withthe bushing.
 8. The panel mounted rotary switch of claim 7, wherein theengagement with the bushing comprises an extrusion on the detentsub-assembly that cooperates with a groove on the bushing.
 9. The panelmounted rotary switch of claim 5, wherein the upper portion of thebushing has a flat side that cooperates with a D shaped opening in thepanel to prevent rotational movement.
 10. The panel mounted rotaryswitch of claim 1, wherein the detent sub-assembly utilizes only onespring and at least one ball to contact rotor cams (cylindrical lobes)thereby setting a switch position.
 11. The panel mounted rotary switchof claim 1 in electrical connection to a plurality of printed circuitboards.
 12. A method of using a rotary switch, comprising: mounting therotary switch to a panel such that a detent sub-assembly is in planarrelation to the panel.
 13. The method of claim 12, wherein the detentsub-assembly is housed in a bushing that extends from beneath the panelto above the panel.
 14. A rotary switch having a detent sub-assemblyhoused in an upper portion of a bushing, a shaft that couples auser-rotatable knob on a upper portion of the shaft, wherein the knob iscapable of being rotated directly by a user without linear movement ofthe shaft, and wherein a rotational movement of the shaft makes anelectrical connection between a first terminal and a second terminal.